It is known that a patch antenna, composed of a driven patch and a parasitic patch structured as two electromagnetic wave radiating layers, has an excellent broad-band performance. By protecting such patch antenna inside a radome, a patch antenna structure leaving the advantages in terms of portability as mobile communication means, reliability, and aesthetic appearance can be provided. For example, such structures are disclosed in Japanese patent application laid-open No.2-141007(1990) and Japanese patent application laid-open No.3-74908(1991), where the former discloses a microstrip antenna in which a parasitic patch is adhered to inner surface of a radome and the latter discloses a stacked microstrip antenna in which a parasitic patch is buried in the wall of a radome.
However, in these conventional patch antennas disclosed a problem is that the number of fabrication steps must increase due to requiring the adhesion of the parasitic patch to the radome or the burying of the parasitic patch in the wall of the radome. Also, it is difficult to position the parasitic patch at a proper position on the radome or in the wall of the radome.